A wide variety of closures are known for closing and sealing bottles and other like containers. One type of closure is typically provided with internal threads on its side wall portion which are adapted to engage external threads on the neck of the container for retention of the closure on the container. Rotation of the closure with respect to the container results in the closure moving axially of the bottle neck so that the closure may be removed and the container opened. Other types of closures include arrangements for interlocking with the necks of the containers to which they are applied with little or no relative rotation by way of a snap fitting or the like.
One desirable feature for closures of the above descriptions is a provision for indicating whether the container has been previously opened by removal of the closure therefrom. To this end, various arrangements for so-called pilfer bands are known. These arrangements are sometimes referred to as tamper bands, guarantee bands, or security rings. Frequently, a peripherally extending annular locking ring or other arrangement is provided on the neck of the container for interaction with the pilfer band of the closure for indication of closure tampering.
For a closure made from plastic material, it is desirable that the pilfer band be formed integrally with the shell or cap portion of the closure. When the closure is applied to a container, the integral pilfer band portion of the closure is typically brought into association with the annular locking ring or other arrangement provided on the neck of the container so that the pilfer band operatively interacts therewith for indicating whether the closure has been removed from the container.
Because the application of closures to containers is preferably performed on a high speed production line, it is desirable that application be possible with the fewest number of production steps. Heretofore, the pilfer band arrangement for some plastic closures has required one or more specific production processes for properly associating the pilfer band arrangement with the locking ring or other retaining means provided on the neck of the container.
For instance, U.S. Pat. No. 3,673,671, issued to Lietz, illustrates a method of applying pilfer-proof closures wherein a security ring provided on a plastic closure is deformed by heat and pressure to roll it onto an undercut portion of the neck of the container. Similarly, U.S. Pat. No. 4,033,472, to Aichinger, illustrates a closure for containers having a downwardly depending band of heat deformable thermoplastic which is heat deformed so as to engage with a bead provided on the container neck.
Another type of heat-deformable pilfer band arrangement is illustrated in British Pat. No. 1,384,370, issued to Behringer, et al. This patent teaches a closure with an integral heat-shrinkable pilfer-band comprising resilient memory plastic which is flared outwardly for application of the closure to a container, and is then heated, in a heat tunnel for example, whereby the resilient memory of the band causes it to "shrink" and deform so as to engage an annular locking ring on the container rack.
Clearly, the drawbacks of plastic closures of this type will be readily appreciated in that not only does the application of these types of closures require additional production steps in a high speed bottling operation, but additionally mandate that the bottler or other packager provide the requisite specialized machinery for application of the closures in the prescribed fashion.
Thus, the development of an effective, self-engaging pilfer band for a plastic closure which would be suitable for application to bottles or other like containers without the use of specialized production equipment would significantly enhance the desirability of plastic closures for use in a high speed bottling operation.